Isotactic polypropylene (iPP): ethylene propylene diene monomer (EPDM) blend is one of the most suited compatible and miscible blends. The blends of iPP and EPDM (80:20) filled with BaCO3 nanoparticles (0.5, 1.5, 2.5 and 3 wt%) were prepared on Brabender Plasticorder, which was then subjected to injection molding to get dumbbell-shaped specimens. Meanwhile, BaCO3 nanoparticles (nBaCO(3)) were prepared using ultrasonic cavitation technique. The size and shape of nBaCO(3) particle was confirmed using transmission electron microscope and found to be capsule shape of diameter similar to 40-60 nm with aspect ratio (l/d) of 2.2-2.5. The reduction in particle size of nBaCO(3) leads to formation of uniform suspension. The solution was kept as such for long time so as to nullify the charges developed over the surface of nanoparticles. The mechanical properties of nBaCO(3)-reinforced iPP-EPDM blends were studied using universal testing machine and impact tester. Moreover, thermal properties were studied using flammability tester, vicat softening temperature, thermo gravimetric analyzer and differential scanning calorimeter (DSC). Dispersion of nBaCO(3) in iPP-EPDM matrix was studied using scanning electron microscope and X-ray diffractometer. The mechanical and thermal properties of iPP-EPDM/nBaCO(3) blends were found to be improved significantly with increasing amount of nBaCO(3) up to 2.5 wt%, which is due to good compatibility in between iPP and EPDM with uniform dispersion of nBaCO(3). Moreover, due to agglomeration at 3 wt% loading of nBaCO(3) few of the properties found to be decreased marginally.